Overcurrent protection and fault isolation

A computer program product including a non-transitory computer readable medium storing instructions for causing a computer to implement an overcurrent fault protection method, the method comprising:

• detecting an overcurrent fault in a variable frequency electric power generation system (VF EPGS) having a first main generator coupled to a first alternating current (AC) bus through a first generator line contactor (GLC), a second main generator coupled to a second AC bus through a second GLC and an auxiliary generator coupled to a plurality of bus tie contactors (BTCs), through a third GLC, and coupled to at least one of the first and second AC buses through the plurality of BTCs;
• locking out one or more of the plurality of BTCs in response to the detection of the overcurrent fault;
• and
• opening at least one of the first second and third GLCs in response to a continued detection of the overcurrent fault;
• locking out a first subset of the plurality of BTCs coupled between the auxiliary generator and the first AC bus in response to the auxiliary generator powering the first AC bus;
• opening the third GLC and shutting down the auxiliary generator in response to the continued detection of the overcurrent fault after a predetermined time delay;
• and
• locking out a second subset of the plurality of BTCs coupled between the auxiliary generator and the second AC bus.

A variable frequency electric power generation system (VF EPGS), comprising:

• a first generator coupled to a first generator control unit (GCU) and to a first alternating current (AC) bus through a first generator line contactor (GLC);
• a second generator coupled to a second GCU and to a second AC bus through a second GLC;
• and
• an auxiliary generator coupled to a third GCU and to a plurality of bus tie contactors (BTCs), through a third GLC, and coupled to at least one of the first and second AC buses through the plurality of BTCs,
• wherein the first, second and third GCUs are configured to:
• detect an overcurrent fault;
• lock out one or more of the plurality of BTCs in response to detecting the overcurrent fault;
• open at least one of the first second and third GLCs in response to a continued detection of the overcurrent fault;
• lock out a first subset of the plurality of BTCs coupled between the auxiliary generator and the first AC bus in response to the auxiliary generator powering the first AC bus;
• open the third GLC and shutting down the auxiliary generator in response to the continued detection of the overcurrent fault after a predetermined time delay;
• and
• lock out a second subset of the plurality of BTCs coupled between the auxiliary generator and the second AC bus.